多本构模型耦合的数值模拟方法及其在锥齿轮等温锻造过程中的应用

发布时间：2018-05-17 22:35

本文选题：锥齿轮 + 等温锻造　；参考：《山东大学》2017年硕士论文

【摘要】：锥齿轮是一种齿顶呈圆台形的齿轮,常成对使用,可改变传动轴的方向,广泛应用于机械传动装置中。由于其特殊的锥形结构,锥齿轮特别适合采用锻造方法生产,所生产出来的齿轮内部组织连续、机械性能较好、寿命长,但传统的锻造方法依然存在设备及模具所受载荷过大、齿腔填充不饱满、后续机械加工余量大等问题。而采用等温锻造方法,则是将模具加热到与坯料相同或相近的温度,伴以较低的变形速率,给予材料充足的时间发生动态回复与动态再结晶,从而显著提高材料的流动性能,同时减小模具所受的应力,所生产出的锥齿轮具有组织均匀、尺寸精度高等优点。等温锻造作为一种锥齿轮的精密锻造方法,能够很好地提高锻造锥齿轮的使用性能,因此具有重要的研究价值和实际意义。数值模拟方法是研究金属塑性成形过程的重要分析手段。对锥齿轮等温锻造过程进行数值模拟,可较准确地预测材料的变形情况及成形载荷等,从而大大降低产品的生产周期。而确定材料的应力与应变、应变速率等变形参数之间的关系模型,即本构模型,对于模拟结果的准确性具有非常重要的影响。本文针对20CrMnTi锥齿轮等温锻造过程,研究了多本构模型耦合的数值模拟方法,对材料变形过程中所处的状态进行区分,并分别采用不同的本构模型。相比于使用单一而复杂的本构模型,采用该方法可以使模拟结果更符合实际情况。首先,针对锥齿轮零件进行了等温锻造成形工艺分析,利用UG软件绘制了三维零件图和锻件图,同时制定了锥齿轮等温锻造的生产工艺方案。然后,以20CrMnTi等温锻造成形温度为试验温度,以不同的压缩速率分别对其进行等温压缩试验;对得到的数据分别进行了压缩速率修正、光滑处理和行程修正;根据试验结果中材料应力-应变曲线呈现的动态回复和动态再结晶特征,将材料变形过程分为硬化状态、软化状态和稳态,并分别构建三种状态下的本构方程及其临界点的参数方程;将三个本构方程编写为程序代码,并嵌入到Deform子程序中,从而实现了基于多本构模型耦合的Deform软件二次开发。随后,使用得到的程序对锥齿轮等温锻造过程进行数值模拟,分析了金属流动、成形载荷以及材料所处状态等情况,研究了不同飞边大小、锻压速度等工艺条件对锥齿轮成形效果和成形载荷的影响。最后,根据所选择的成形设备,设计并加工了一套锥齿轮等温锻造模具及温控装置,进行了锥齿轮等温锻造实验,观察锻件成形效果并记录载荷的变化,验证了所设计的锥齿轮等温锻造工艺及模具的合理性。
[Abstract]:Bevel gear is a kind of gear with round top, which is often used in pairs. It can change the direction of drive shaft and be widely used in mechanical transmission. Because of its special conical structure, bevel gear is especially suitable for production by forging method. The produced gear has continuous internal structure, good mechanical properties and long life. However, the traditional forging method still has too much load on the equipment and die. Tooth cavity filling is not full, follow-up machining allowance is large, and so on. By means of isothermal forging, the mold is heated to the same or similar temperature as the blank, accompanied by a lower deformation rate, and the material is given sufficient time for dynamic recovery and dynamic recrystallization, thus significantly improving the fluidity of the material. At the same time, the bevel gear produced by reducing the stress of die has the advantages of uniform structure and high dimensional precision. Isothermal forging, as a precision forging method for bevel gears, can improve the performance of bevel gears, so it has important research value and practical significance. Numerical simulation method is an important analytical method for the study of metal plastic forming process. The numerical simulation of isothermal forging process of bevel gear can accurately predict the deformation and forming load of the material, thus greatly reducing the production cycle of the product. The relationship between stress and strain, strain rate and other deformation parameters, i.e. constitutive model, is very important to the accuracy of simulation results. Based on the isothermal forging process of 20CrMnTi bevel gear, the numerical simulation method of coupling multi-constitutive model is studied in this paper. The states in the process of material deformation are distinguished, and different constitutive models are adopted respectively. Compared with the simple and complex constitutive model, this method can make the simulation results more realistic. Firstly, the isothermal forging process of bevel gear parts is analyzed, 3D parts drawing and forging drawing are drawn by UG software, and the production process scheme of isothermal forging of bevel gear is established. Then, the 20CrMnTi isothermal forging temperature is used as the test temperature, and the isothermal compression test is carried out at different compression rates, and the compression rate correction, smoothing treatment and stroke correction are carried out respectively. According to the dynamic recovery and dynamic recrystallization characteristics of the stress-strain curves in the experimental results, the deformation process of the materials is divided into hardening, softening and steady-state. The constitutive equations in three states and their critical point parameter equations are constructed, and the three constitutive equations are written as program code and embedded into Deform subprograms, thus realizing the secondary development of Deform software based on the coupling of multiple constitutive models. Then, the isothermal forging process of bevel gear is simulated by using the program. The metal flow, forming load and material state are analyzed, and different flange sizes are studied. The influence of forging speed and other technological conditions on bevel gear forming effect and forming load. Finally, according to the selected forming equipment, a set of isothermal forging die and temperature control device for bevel gear are designed and machined, the isothermal forging experiment of bevel gear is carried out, the forming effect of forging is observed and the change of load is recorded. The isothermal forging process of bevel gear and the rationality of die are verified.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH132.41;TG316

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